As this type of apparatus, there is known a hybrid vehicle, provided with: an electric motor in addition to an internal combustion engine as a power source; a generator for generating electric power by the power of the internal combustion engine; and a battery capable of storing electric power generated by the generator. In this type of hybrid vehicle, the power of the internal combustion engine is divided by a power dividing mechanism made of e.g. a planetary gear, into the rotating shaft of the generator and a drive shaft coupled with an axle.
In this type of hybrid vehicle, in order to increase the transmission efficiency of energy from the internal combustion engine to the drive shaft, there is known such a technology that if a target drive torque to be outputted to the drive shaft is less than the maximum output torque of the internal combustion engine, the rotating shaft of the generator is mechanically locked to mechanically and directly connect the drive shaft and the output shaft of the internal combustion engine. According to the technology, the power of the internal combustion engine can be directly outputted to the drive shaft without through the generator and the electric motor, so that it can eliminate the occurrence of an energy loss in the generator and the electric motor and can increase the transmission efficiency. For example, a patent document 1 or the like discloses a technology in which if the mechanical lock of the rotating shaft of the generator is unintentionally released, the mechanical lock of the generator is uniformly forbidden after the release. Moreover, a patent document 3 or the like discloses a technology in which if it is detected that foreign substances enter in an oil control valve (OCV) for controlling a valve of the internal combustion engine, an electric current applied to the OCV is alternately changed between the maximum current and the minimum current to flush out the foreign substances with hydraulic oil by an oil pump.    Patent document 1: Japanese Patent Application Laid Open No. 2004-345527    Patent document 2: Japanese Patent Application Laid Open No. 2002-51407    Patent Document 3: Japanese Patent Application Laid Open No. 2001-234768